Vinyl ester resins which are normally prepared by reacting about equivalent amounts of an unsaturated monocarboxylic acid with a polyepoxide contain aliphatic hydroxyl groups as a result of the resin forming reaction between the carboxyl and epoxide groups. These resins have many valuable uses, particularly when combined with other copolymerizable monomers. For many uses such as glass fiber reinforced pipes, vessels, laminates and the like, styrene and like aromatic monomers are greatly preferred. While the resins are compatible with such monomers as styrene they form cloudy solutions at high monomer concentrations. This invention extends the solubility or compatibility of vinyl ester resins to such concentration ranges.
To reduce the viscosity of solutions of high molecular weight, usually solid resins in inert solvents, U.S. Pat. No. 3,804,795, converts hydroxyl groups in the resin to acetal and ketal groups by a similar reaction. Vinyl ester resins are generally low molecular weight, usually liquid, resins. However, the improved solubility of the modified resins of this invention in styrene and like monomers is an unexpected and beneficial advantage.